docs: def count_unread_messages_between(self, um_to_user, um_from_user):
          """
          Returns the amount of unread messages between two users
  
          :param um_to_user:
              A Django :class:`User` for who the messages are for.
  
          :param um_from_user:
              A Django :class:`User` from whom the messages originate from.
  
          :return:
              An integer with the amount of unread messages.
  
          """
          unread_total = self.filter(message__sender=um_from_user,
                                     user=um_to_user,
                                     read_at__isnull=True,
                                     deleted_at__isnull=True).count()
  
          return unread_total